The capped wheel nut assembly of the present invention is designed to replace the construction presently in use in which the cap is welded to the nut. According to the present invention, the cap is secured to the nut by adhesive.
Usually in a capped wheel nut assembly, the nut is steel with a zinc plate and the cap is stainless steel. A welded joint between the nut and cap is a corrosive site because of the different metals involved. Elimination of the welded joint eliminates these corrosive sites which lead to weakening or failure of the bond. Elimination of the welded joint also eliminates stress risers in the cap which are caused by the welding of the cap to the nut.
The adhesive bond of the present invention insulates the two metals from each other and thus resists corrosion.
The adhesive bond also imparts flexibility and thus eliminates rattle.
It has been found that an adhesive bond also produces a much lower on/off failure rate, that is, the capped wheel nut assembly may be applied and removed from a bolt many more times than a welded nut before failure.
The adhesive employed in the present invention is one which retains its adhesive character over a wide range of temperatures, preferably a silicon adhesive.
Not only will a welded capped wheel nut assembly corrode, but often the weld sites will show through. Thus an adhesive bond will improve the appearance of the wheel nut assembly because of the elimination of the weld and of the distortion due to high pressures associated with a welding operation.
As another feature of the invention, the open end of the cap has an enlarged marginal portion that is crimped over a circular enlargement near one end of the nut. This improves axial retention which is important because there is a tendency for an impact wrench to ride up and pull the cap off the nut. The crimp also reduces stress concentration. Stress at the open end of the cap can sometimes cause the cap to split.
Other advantages and features of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.